The primary objectives of this study are threefold: (1) to characterize the enzyme(s) and/or enzyme systems involved in turnover of lung connective tissue precursor molecules; (2) to relate the turnover of these moleculaes to normal lung connective tissue development; and (3) to gain insights into the possible mechanisms which control lung connective tissue precursor synthesis and degradation. Enzyme activity in rabbit and hamster lung from early postnatal to adulthood will be studied and compared in patterns in an in vivo model of accelerated lung growth (post-pheumonectomy in rabbit) and an in vivo model is important in that it supplies a period of rapid lung growth over which enzyme activities can be correlated. An additional goal of this study will be to monitor the synthesis of connective tissue precursor molecules and their associated "precursor-degrading enzymes" by immunologic techniques using specific antisera. The insights gained in these studies of normal and compensatory lung growth will provide foundations for subsequent studies of intra and extra cellular control mechanisms of lung connective tissue.